Oxygen Inhibition in Dental Resins

Abstract

Oxygen inhibits free radical polymerization and yields polymers with uncured surfaces. This is a concern when thin layers of resin are being polymerized, or in circumstances where conventional means of eliminating inhibition are inappropriate. In this study, we tested the hypothesis that viscosity, filler content, and polymerization temperature modify oxygen diffusion in the resin or the reactivity of radical species, and affect the degree of conversion near the surface. Confocal Raman micro-spectroscopy was used to measure monomer conversion from the surface to the bulk of cured resins. Increased viscosity was shown to limit oxygen diffusion and increase conversion near the surface, without necessarily modifying the depth of inhibition. The filler material was shown to increase, simultaneously, oxygen diffusivity and the viscosity of the resin, which have opposite effects on conversion. Polymerization at a temperature above approximately 110 degrees C was shown to eliminate oxygen inhibition.

Effect of Surface Treatments on Microtensile Bond Strength of Repaired Aged Silorane Resin Composite

“…3 A silorane molecule comes from the reaction of oxirane and siloxane molecules. 3,6,7 Whereas the polymerization process of methacrylate composite occurs via free radical polymerization, 8,9 the polymerization of silorane composite is generated by the cationic ring-opening polymerization of the oxirane molecule. The silorane composite has two main advantages: low polymerization shrinkage due to the ring-opening polymerization of the oxirane monomer and increased hydrophobicity because of the siloxane molecule.…”

Influence of Post-Bleaching Time Intervals Using 37% Carbamide Peroxide on Dental Substrate Adhesion

“…This is probably due to the residual oxygen concentration (BARCELLOS, 2010;BERGER, 2013;CANNABRAVA, 2014;GAUTHIER, 2005), regardless of whether or not the bleaching agent is directly in contact with the restored surface. It occurs because the active substance of 37% carbamide peroxide, which is hydrogen peroxide, undergoes decomposition and releases free radicals, which react with the macromolecules responsible for darkening the teeth, such as iron sulfide and hydrogen released (FÉLIZ-MATOS, 2014).…”

“…Thus, the residual oxygen can inhibit resin polymerization and, as a result, decrease the bond strength of the restorative material (GAUTHIER, 2005;BARCELLOS, 2010). Besides, a marginal microinfiltration increasing may occur due to defective marginal closure (KUMAR, 2015).…”

The influence of light intensities irradiated directly and indirectly through resin composite to self-etch adhesives on dentin bonding

“…When light-cured resin composite is irradiated, the hydrophobic resin matrix of the filled resin composite can co-polymerize with the uncured bonding resin produced on cured bonding layer 20) as well as polymerizing itself. Solvents in one-step self-etch adhesives retard the polymerization process [21][22][23] , leading to the creation of thicker oxygen inhibited uncured layer on the cured bonding resin [20][21][22] . Presumably, there would be remnants of water/solvent in the uncured bonding layer of a one-step self-etch adhesive.…”

“…This uncured bonding resin layer becomes a site for co-polymerization with the uncured matrix of the resin monomers of the resin composite 20) . In the case of a one-step self-etch adhesive, residual water/solvents may be present within the uncured bonding resin layer, which might affect co-polymerization between the bonding resin and resin composite, because the presence of residual water/solvents causes a reduction in the degree of conversion [21][22][23] . Therefore, the bonding of one-step self-etch adhesives might be influenced by the intensity of the light irradiation directly and indirectly through the resin composite more than two-step self-etch adhesives with a solvent-free bonding agent.…”